Protective liner for autoclaves



Mflmh 1953 J. H. BOIVINET PROTECTIVE LINER FOR AUTOCLAVES Filed June 7,1948 Fiel- INVEN 1 OR ATTORNEY Patented Mar. 31, 1953 UNITED STATESPATENT OFFICE PROTECTIVE LINER FOR AUTOCLAVES ration of FranceApplication June 7, 1948, Serial No. 31,559 In France June 16, 1947Claims.

Autoclave containers of the type used in the chemical industry arerequired to possess both mechanical resistance to stresses to which theymay be subjected, in use and chemical resistance to the corrosive actionof the materials they are to contain.

It is not always practicable to fulfil both the above conditions throughthe use of a metal or of only one metal. In general, a metal will besufiiciently resistant mechanically but will not resist corrosion, or,if it does withstand corrosion, it will not show sufficient resistanceto mechanical stresses.

Certain substances (such as soft metals, plastics and the like), resista large number of chemical reactions, but their tensile resistance isvery low.

This leads to the idea of using such substances as internal liners forcontainers the shell of which consists of a metal having a sufficientresistance to mechanical stresses.

In structures of such type, there are certain precautions to be takenand in particular it is necessary that any gases or liquids, entrappedbetween the liner or coating material and the wall of the stressedshell, be capable of escaping towards the outer atmosphere. In theabsence of such a precaution, there would occur, between the liner andthe shell, a succession of alternate compressions and expansions whichwould quickly result in a breakdown of the liner and, as a consequence,the resulting breakdown of the shell of the apparatus, since thechemical agents will then be capable of coming into contact with thelatter.

The present invention is concerned with a method of protecting anautoclave by means of an internal liner, which overcomes the abovedrawbacks.

Said method is characterized in that the protective liner, which ispreliminarily prepared separately, is applied to the wall of thecontainer by a pressure which is Very gradually exerted from theinterior of the container, with the interposal of a device for ventingor draining any gases or liquids from between the wall of the containerand the liner.

There will be described hereinafter by way of example, the procedure forinternally lining a cylindrical container with a lead liner. It will beobvious that the liner might also be formed of any other suitablematerial such as tin, silver, various metals and alloys, plasticmaterials such as vinyl chloride, and so on.

The accompanying drawing illustrates by way of example one embodiment ofthe invention:

Fig. 1 is a fragmentary view in longitudinal cross section of anautoclave including an internal protective liner embodying theinvention.

Fig. 2 is a transverse cross section online .2...,- 2 of Fig. 1.

Fig. 2a is a similar view of a modification, and

Fig. 3 is a view on an enlarged scale oia-por: tion of Fig. 2.

As shown in Fig. 1, the autoclave comprises-a cylindrical shell I madeof a metal possessing sufficient resistance to mechanical stresses; saidshell is provided at each end thereof with an annular flange 2; the endcovers 3 are adapted to be secured to said flanges by means of bolts.

Metal bars 4 are arranged to. extend along the generatrices of theinternal surface of the shelll. Said bars preferably have a roundedcrosssection, being for instance of the commercially available halfroundsection type; the rounded portion of the barsections is directedinwardly,

while the flat portion thereof is slightly grooved throughout its entirelength with a shallow and narrow channel 5. Saidchannel is placed incommunication with the atmosphere either through small apertures ll,perforated through the shell 5, or through apertures formedbetw'een theflanges 2 of the shell and the covers 3. Between each successive pair ofsaidbars there is arranged a wire mesh 6 of relatively large mesh size(see Fig. 3).

The barsB and the mesh 6 may be maintained in place by the provision ofa few spotwelds, as for instance at S. The mesh 6 or the M1754 might beused alone, depending on the sizes and shapes of the apparatus. v

There is then inserted into the container the cylindrical lead liner it,which is to form the internal coating of the container and which hasbeen formed and welded separately. Said liner should have an externaldiameter very slightly smaller than the diameter of the circumferencewhich is internally tangent to the longitudinal bars t. There may bepreferably formed in the lead liner, which in this case will be formedwith a diameter equal to the internal diameter of the apparatus, a foldhaving very carefully rounded curvatures adapted to facilitate theinsertion of the liner into the apparatus (as shown at l2 in Fig. 2a).

The edges 1 of the liner are folded back (see Fig. 1) into the recessprovided for that purpose in each of the flanges 2. Said folded edges donot entirely fill said recess, and the sealing of the liner is completedwith a wiped plumbing joint. If the liner includes a preliminarilyformed fold l2; it should be carefully hammered down at both ends of thecylinder, so as to properly apply the lead liner at both ends thereofagainst the internal surface of the apparatus and facilitate the foldingback of its edges.

Moreover, the end covers will have preliminarily been plumbed with awiped joint and the surface of the lead which is to engage the flanges 1is rectified. If tube connections 9 are to be provided, the latter arefilled with molten lead and the perforation is made with a drill. Theend covers 3 are put into place with the interposal of a lead lining 8and are carefully bolted in position.

The autoclave is then filled with water, steam or a gas at a suitabletemperature allowing for a certain amount of extension in the materialconstituting the liner and, by means of a test pump, the pressure isvery gradually built up to a value in excess of the normal operatingpressure. It is essential that said pressure increase should be effectedvery slowly, thereby enabling the liner I to be applied very uniformlyin the first place upon the bars 4, then, by a very gradual and uniformextrusion effect exerted between two edges of adjacent bars 4, againstthe wire mesh 6. Since, as stated above, the wire mesh is of relativelylarge mesh size, the plastic lead metal of the liner is eventuallyextruded through the mesh openings as the internal pressure is built upinside the autoclave, and the extruded metal is applied against theinterior surface of the shell. The air entrapped between the lead linerl0 and the inner wall I of the autoclave is thus very gradually forcedout through all of the apertures provided to that end.

The above described device furthermore makes it possible to immediatelydetect the presence of any leakage in the lead liner. The gases orliquids, contained in the autoclave, should by any accident the leadliner be perforated, will follow the path followed by the air in thecoating operation. They will then appear at the outlet of any one of thevents and this will be a warning to halt the operation of the apparatusin ample time to prevent the corrosion of the metal forming the shellreaching an excessive value.

The method and protective device described above involving a lead linerare particularly suitable for the construction of apparatus or parts ofapparatus to be used in the synthetic manufacture of urea from carbonicacid gas and ammonia.

What I claim is:

1. The method of lining an autoclave shell, subjected in normaloperation to mechanical stresses and corrosive action, with a smoothcorrosion resisting lining, comprising the steps of: disposing spacingmeans at intervals on the interior of the shell; introducing into theshell a cylindrical, unitary, deformable, open-ended lining having adiameter smaller than the internal diameter of said shell; securing thecylindrical edges of said lining to both ends of said shell; closing oilboth ends of the shell; gradually applying fluid pressure in excess ofthe normal operating pressure to the interior surface of said lining,whereby the entire unsecured part of said lining is progressivelydeformed and applied against the spacing means and against amultiplicity of uniformly distributed areas on the interior surface ofthe shell, and simultaneously expelling to the atmosphere any fluidentrapped between the lining and the shell.

2. An autoclave comprising an outer shell resistant to mechanicalstresses, a unitary, smooth, corrosion-resisting deformable inner liningsubstantially continuous with and coextensive in area with the innersurface of said shell, separate spacing means between said shell andlining uniformly distributed over the entire circumference of saidshell, said lining contacting the inner surface of the shell at amultiplicity of areas uniformly distributed over the entire innersurface, and venting means connecting the space between the liner andthe shell to the outer atmosphere whereby, in normal operation, thespace between the shell and lining is substantially free of fluid.

3. An autoclave according to claim 2, in which the spacing meanscomprise a wire mesh.

4. An autoclave according to claim 2, in which the spacing meanscomprise a plurality of bars disposed along the inner circumference ofthe autoclave and extending parallel to the longitudinal axis of theautoclave.

5. An autoclave according to claim 2 in which the bars comprise shallowgrooves communicating with the venting means.

JEAN HENRI BOIVINET.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 341,435 Russell May 4, 1886353,731 Bremaker Dec. 7, 1886 390,727 Wagg Oct. 9, 1888 1,651,521Girardville Dec. 6, 1927 1,892,433 Huif Dec. 27, 1932 1,894,116 PierJan. 10, 1933 1,911,608 Davis et a1 May 30, 1933 1,940,277 Stresau Dec.19, 1933 2,100,895 Austin Nov. 30, 1937 2,329,970 Zimmerman Sept. 21,1943 2,428,542 Bernhardt Oct. 7, 1947 2,460,820 Hagopian Feb. 8, 1949

2. AN AUTOCLAVE COMPRISING AN OUTER SHELL RESISTANT TO MECHANICALSTRESSES, A UNITARY, SMOOTH, CORROSION-RESISTING DEFORMABLE INNER LININGSUBSTANTIALLY CONTINUOUS WITH AND COEXTENSIVE IN AREA WITH THE INNERSURFACE OF SAID SHELL, SEPARATE SPACING MEANS BETWEEN SAID SHELL ANDLINING UNIFORMLY DISTRIBUTED OVER THE ENTIRE CIRCUMFERENCE OF SAIDSHELL, SAID LINING CONTACT THE INNER SURFACE OF THE SHELL AT AMULTIPLICITY OF AREAS UNIFORMLY DISTRIBUTED OVER THE ENTIRE INNERSURFACE,